Docker DIND unable to access private registry

Question

I am using GitLab along with GitLab runner and DIND.

Configuration details:

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docker run --privileged --name gitlab-dind -d --restart=always docker:17.07-dind

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cat gitlab_runner.sh
docker run -d --name gitlab-runner --restart always \
  -v /mnt/data/gitlab/gitlab-runner:/etc/gitlab-runner \
  --link gitlab-dind:docker \
  gitlab/gitlab-runner:v9.5.0

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cat /mnt/data/gitlab/gitlab-runner/config.toml
concurrent = 1
check_interval = 0

[[runners]]
  name = "RunnerA"
  url = "https://gitlab.dev.abc.net"
  token = "d8ed43a69ebed74ccab2493857d8cb"
  executor = "docker"
  [runners.docker]
    tls_verify = false
    image = "docker:17.07"
    privileged = false
    disable_cache = false
    volumes = ["/cache"]
    host = "tcp://gitlab-dind:2375"
    shm_size = 0
  [runners.cache]

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cat ~/wksp/test-proj/.gitlab-ci.yml
image: docker.artifactory.abc.net/docker:17.07

variables:
  DOCKER_HOST: tcp://docker:2375

# This before_script block was added later but it seems this block
# isn't executed before the DIND tries fetching image from Artifactory
before_script:
  - docker login -u svc-art-user -p some-pwd docker.artifactory.abc.net
  - docker info

services:
- docker.artifactory.abc.net/docker:17.07-dind

build:
  stage: build
  script:
  - docker build -t my-docker-node-image .

---------------------------------------

As an aside, in the above configuration, is DOCKER_HOST config needed in .gitlab-ci.yml or just the entry ( host = "tcp://gitlab-dind:2375 ) in config.toml suffice?

Now when the runner runs, i get the following error:

Runner log error:
Running with gitlab-ci-multi-runner 9.5.0 (413da38)
  on RunnerA (d8ed43a6)
Using Docker executor with image docker.artifactory.abc.net/docker:17.07 ...
Starting service docker.artifactory.abc.net/docker:17.07-dind ...
Pulling docker image docker.artifactory.abc.net/docker:17.07-dind ...
ERROR: Preparation failed: Error response from daemon: Get https://docker.artifactory.abc.net/v2/: x509: certificate signed by unknown authority

I may be wrong but it seems this error is because the service account ( svc-art-user ) isn't able to login before the DIND image pull happens.

Answer 1

You need to provide authentication details to your Gitlab Runner because it needs to pull the image.

You need to create DOCKER_AUTH_CONFIG secret variable with the authentication details as below

{
     "auths": {
         "docker.artifactory.abc.net": {
             "auth": "bXlfdXNlcm5hbWU6bXlfcGFzc3dvcmQ="
         }
     }
 }

This you can get by logging into docker locally and and checking ~/.docker/config.json

The documentation provides good details on this

https://docs.gitlab.com/ce/ci/docker/using_docker_images.html#define-an-image-from-a-private-docker-registry

https://docs.gitlab.com/runner/configuration/advanced-configuration.html#using-a-private-container-registry